Columnar display for electrical signals with digital signal limit set

ABSTRACT

A system for displaying the level of a variable electrical signal is disclosed, in which the variable electrical signals are converted into digital form, which are in turn decoded and arranged to consecutively activate a vertical series of indicator elements up and down the series in response to increases and decreases respectively in the digital signal, and with any preceding activated element being deactivated so that only a single individual indicator element corresponding to each digital signal is activated. Accordingly, the rise and fall of the position of the activated indicator element indicates the level of the electrical signal. An arrangement is also disclosed for providing signal limit indication comprising means for comparing the digital signal corresponding to the variable electrical signal with preset digital limit signals which means drives a limit indicator element whenever the generated digital signal is outside the preset values.

United StatesPatent [191 Tumbush July 23, 1974 COLUMNAR DISPLAY FOR ELECTRICAL Primary Examiner-Alfred E. Smith SIGNALS WITH DIGITAL SIGNAL LIMIT Assistant Examiner-Ernest F. Karlsen 7 SET Attorney, Agent, or Firm-John R. Benefiel [75] Inventor: Gerald Tumbush, Xenia, Ohio [73] Assignee: The Bendix Corporation, Southfield, [57] ABSTRACT Mich. A system for displaying the level of a variable electrical signal is disclosed, in which the variable electrical [22] led: 1972 signals are converted into digital form, which are, in 21 App]. 243 49 turn decoded and arranged to consecutively activate a vertical series of indicator elements up and down the series in response to increases and decreases respec- [52] US. Cl. 324/103 P, 324/96, 324/122 tively in the digital signal and i any preceding i [51] 111i. C1. G01! 19/ 16, G011 13/02 vated element being deactivated so that only a i l [58] held of Search 324/103 P1 103 1 individual indicator element corresponding to each 324/9911! 157, 99 1 digital signal is activated. Accordingly,- the rise and fall of the position of the activated indicator element indi- [56] References cued cates the level of the electrical signal. An arrangement UNITED STATES PATENTS is also disclosed for providing signal limit indication 2,486,890 11/1949 Stanmyre ..'324/103 R comprising means for comparing the digital signal cor- 2,536,806 1/1951 Hansen, Jr. 324/157 responding to the variable electrical signal with preset 3,64 959 King, Jr. 324/99 D 1 digital limit signalswhich means drives a limit indica- 3,108,470 11/1963 Martin 324/122 to element whenever the generated ignal is 3,440,537 4/1969 Warner et al.. 324/99 R outside the preset va|ues 3,488,589 l/l970 Kintner 324/99 R 9 Claims, 8 Drawing Figures 352 :g- 13-4 O EQ- x Z6 20/ jg-2 E? 6i 3- PMEMED LP Y 3.825.827

SHEET 3 UF' 5 w /o FIGS CQ/Yl ERTER CONVER R CO/VVERER FIGB I I OVER 194N625 Z8 COLUMNAR DISPLAY FOR ELECTRICAL SIGNALS WITH DIGITAL SIGNAL LIMIT SET BACKGROUND OF THE INVENTION 1. Field of the Invention This invention covers signal readout devices and more particularly concerns devices for displaying the level of variable electrical signals in a columnar form.

. 2. Descriptionof the Prior Art In arrangements forinspecting workpieces on a production basis in which various parameters such as dimensional values are to be compared with upper and lower limits, it has been found to be advantageous to display the signals generated by the measuring transducer in columnar form; i.e., as the signal value increases and decreases, a corresponding indicator rises and falls relative to a vertical scale. This is because of the relative ease and accuracy of reading such displays as compared with ordinary meter type instruments. Furthermore, often there are a number of parameters measured simultaneously and such column type instruments are then ganged with each instrument measuring a separate parameter, and in this situation, the colum- 'nar display allows rapid scanning of the value of each of these parameter values to determine which of these if any are outside the preset value limit. v

I I-Ieretofore, this type of signal display has been limited to air gauge type instrumentation, since only in airflow type gauges in which a float element rises and falls in a vertical transparent tube has such a display been attainable at reasonable cost. Various attempts at such a display for electrical signals have involved relatively bulky, complex, and unreliable apparatus which has also been excessively costly, so that wide commercial acceptance thereof has not occurred.

In addition, the widespread use of such air-flow gages has led to a preference among users for the float type indication, and heretofore such electrical apparatus have not produced a read-out which is similar in appearance to an air-flow gage float.

Since in many situations electrical sensing of these parameters is preferable to air gauging it would be advantageous if such a display could be provided at a reasonable cost if it was not unduly cumbersome and/or unreliable, and it would be preferable if the indication produced the same visual effect as an air gage float.

In most such sensing arrangements, the variable electrical signals are produced in analog form; i.e., the magnitude and/or phase of the voltage or current produced by the transducer corresponds to the parameter value. In a visual display system such as that according to the present invention, these signals are converted to digital form for further processing. If a limit system is utilized, that is, an "indication is provided whenever the parameter value reaches a preset value, and if the analog signal is compared to a preset analog value, drift or shifts in the correspondence between the digital signals and the analog signals sometimes occurs, leading to change in the digital value triggering the indicator. This may lead the operator to believe there is a malfunction in the limit set circuit, even though the drift is within the operating tolerance of the instrument.

Therefore, it is an object of the present invention to provide a column display of the level of variable electrical signals without the use of complex, unreliable or excessively costly apparatus, and which produces a visual effect similar to an air gage float.

It is another object of the present invention to provide a limit set circuit which avoids the effects of drift in the analog-digital converter on the digital value corresponding to the limit set.

SUMMARY OF THE INVENTION These and other objects which will become apparent upon a reading of the following specification and claims is accomplished by means for converting the variable level electrical signals into digital form, which digital signals in turn are decoded and arranged to consecutively activate a vertical series of indicator elements up and down the series in responseto increases and decreases in the digital signal respectively and to deactivate the preceding activated indicator element so that a single individual indicator element is activated, corresponding to each digital signal, the relative position of this single indicator element thus indicating the level of the variable electrical signal. An arrangement is also disclosedfor providing signal limit-indication comprising means for comparingthe digital signal generated by the A/D converter with a preset digital limit signal which means drives a limit indicator element whenever the generated digital signal is outside the preset value.

DESCRIPTION OF TI-IE DRAWINGS FIG. 1 is-a perspective view of an instrument utilizing the columnar display according ,to the present invention. v i

FIG. 2 is a perspective view of a group of instruments of the type shown in FIG. 1 as ganged together.

FIG. 3 is a block diagram of the signal processing systern according to the present invention.

FIG. 4 is a schematic diagram of the decoding and driving circuit together with the light emitting'diodes shown in block form in FIG. 3.

FIG. 5 is a schematic diagram of a first embodiment I of a limit circuit shown in block form in FIG. 3.

- embodiment of the limit I terminology will be utilized for the sake of clarity and a specific embodiment. will be described in orderto provide a complete understanding of the invention, but

it is to be understood that the invention is not so limited 4 and may be practiced in a variety of forms and embodiments.

Referring tothe drawings, and particularly FIGS. 1 and 2, a column type display unit 10 is depicted. This unit includes an instrument housing unit 12 containing the instrument electronics, with the housing unit 12 being supported vertically by a pair of support blocks 14 and 16.

The visual display is comprised of a vertical series of indicator elements comprising light emitting diodes (LEDs) 18 arranged adjacent a vertical scale 20, with increments thereof opposite respective LEDs 18. The LEDs are driven to emit for respective digital values corresponding to an incremental value of an input variable level electrical signal by means of circuitry to be herein described so that as the level of the signal increases and decreases the LEDs experience changes of state such that they are activated consecutively up and down the column and the preceding activated LED 18 is deactivated so that a single individual LED is activated for each incremental value of the analog signal thus, the position of the activated LED provides an indication of the level of the electrical signal and gives I the same general appearance as the float element used Whenever the signal value goes beyond the range of the instrument regardless of the limit values, an overrange LED 28 is provided driven by a logic circuit to be described infra to indicate such a reading.

Also included is a centering control including control knob 30 used to apply a bias signal to shift the correspondence between a given analog signal with a given LED for purposes well-known in the art.

As mentioned above, provision is made for ganging several instruments as shown in FIG. 2, in which several instrument housing units 12 are joined together between common support blocks 14 and 16 for simultaneous reading of several parameters. In this arrange- ,ment a common reject indicator light 22 which is lit if any of the parameter values go beyond the preset limits. In this event the operator can conveniently scan each of the housing units 12 to determine the out-oftolerance parameter or parameters.

Thus the advantages of the conventional air-flow column instruments is obtained with the use of electronics. Additionally, the essentially incremental or digital display eliminates any mistakes arising from the necessity for interpolation present in conventional air-flow column instruments.

Referring to FIG. 3, a block diagram of the system electronics accomplishing the above function is shown.

A source of an analog of a variable level electrical signal is shown as a displacement transducer 32. This displacement transducer 32 could for many purposes suited to the present invention be of the differential This signal processing circuitry 34 provides a DC output voltage which is an analog of the displacement sensed by the displacement transducer 32.

According to the present invention, this analog signal is then converted into digital form by converter means including analog-to-digital converter 36, such devices also being well-known in the art and which function to generate corresponding digital signals from the analog signal generated by the transducer 32. For the specific logic and decoding circuits herein described this output comprises a six-bit binary word. One common and suitable approach to the analog digital conversion is to provide means for controlling the counting of clock pulses into a binary register by a comparator circuit which matches the analog signal value against a control signal value which increases incrementally with the counting of each pulse to an extent depending on the amplification built into the converter 36. When these match, pulse counting into the register stops and the count is read into a storage register for use in the decoding and limit logic circuitry described herein.

The decoding and driver circuit 38 reads and deocdes the binary number corresponding to a given analog signal and causes a single respective LED 18 to emit, with increasing and decreasing binary values causing higher and lower LEDs 18 in the column to be activated to produce the effect described above in' which the relative position of the single activated LED provides an indication of the level of the variable electrical signal.

The system is provided with limit indicator means including the limit circuit 40 which compares the binary number with preset digital values for upper and lower limits and triggers the reject indicator 22 in response to generation of digital signal values above or below respectively these preset digital values. It can be seen that since the signal value compared with the limit values is in digital (binary) form, drift occurring in the A/D converter cannot cause a variation in the particular binary number triggering the rejection indicator 22.

The over-range logic 42 also reads the binary number, and provides emitting by the over-range LED 28 whenever it exceeds the binary number corresponding to the maximum range of the instrument.

FIG. 4 depicts the decoder and driver circuit 38 in schematic form which is arranged to read and decode the six-bit binary word contained in the storage register of the A/D converter and drive a respective LED 18.

At the outset, it is noted that a six-bit binard word is capable of representing 0-63 increments corresponding to values of the analog signal. However, for most purposes, a scale comprised of 51 increments is adequate, allowing for a 25 to +25 increment range. Thus, the decoding and driver circuit 38 is arranged to drive a respective LED 18 for binary numbers 07 through 57. This is accomplished by setting the amplification in the A/D converter 36 such that the analog signal corresponding to 25 units produces a binary signal from the converter equal to 07.

The decoder and driver circuit 38 includes octal coverters 44 and 46 which have inputs connected to the output of the A/D converter such that the lowest three digits of the binary number b b and b are connected to octal converter 44 and the highest three digits b b and b are connected to octal converter 46. Octal converter 46 is conventional in the sense that for various binary number o-7 represented at the inputs, a respective output -7 goes to the low state. Octal converter 44 on the other hand is internally connected so that for each binary number 0-7 represented at the input terminals a respective output 0-7 is connected to ground.

. Each of the outputs 0-7 of octal converter 46 is connected to inverters 48-62 and junction transistors 64-78 so that if a respective output O-7 is low the corresponding junction transistor 64-78 is turned on to apply a potential to the respective emitter line 80-94.

The emitter lines 80-94 are connected to the anodes .of groupings of the LEDs 18 as shown, the emitter line These connections causea respective LED 18 designated by decimal 07-57 to emit when the equivalent binarynumber b b is read at the octal converter 44.

and 46 inputs. For example, if binary 000111 equal to decimal 7 is read out of the A/D converter b b and b are'at zero, while b b and b are at 1. Thus all of theoutputs of the octal converter 46 are high orv at a logic one except the zero output which causes a potential to be applied to emitter line 80 which is connected, to the 07 LED. I

Since b b and b are all high for binary 0001 1 1, line 110 only is connected to ground, to thus cause the 07 LED to emit since this completes the circuit thereto.

While line 110 also connects the 15, 23, 31, 39,47, and 55 LEDs to ground, these do not have a potential applied to the anode, hence none of these emit, so that for binary 0001 11 only the 07LED emits. Taking 'a second example, binary 00100 equal to decimal 8, since b is equal to 1 and b and b are equal to zero, only the 1 output is low, causing the line 82 alone to be energized, applying a potential to 08-15 LEDs. However, for binary number 001000, b b and 12 are all zero so that only line 96 is connected to ground. Thus, only the 08 LED is activated because the circuit is complete only Y for this LED.

The net result is that for each binary number 07-57 read at the inputs of octal converters 44-46, a single respective LED 07-57 as indicated has potential applied'to its anode and its cathode to ground to cause it to emit.

As noted, these LEDs are arranged physically on the instrument in vertical sequence with the 07 LED being lowest and the 57 LED being highest.

' It can be appreciated that this matrix of connections with the two octal converters (44 and 46) in effect provide:a conversion means for converting a six-bit binary number into an output pattern of states at points in the matrix unique to each binary number, these states comprising completed circuits at'each point to thus provide a decoding of the binary number and driving of each corresponding LED 18.

Thus, as the level of the variable electrical signal increases the LEDs l8 are consecutively activated upwardly at incremental values thereof, and similarly as the signal level decreases the LEDs 18 are consecutively activated downwardly. It will of course be understood that if the signal levelvaries rapidly by several increments a subsequent LED 18 in one direction or the other (i.e., upwardly or downwardly) will be activated rather than a strictly consecutive activation. Since the decoder and driver circuit 38, provides for only a single activated LED 18, any preceding activated LED is deactivated as the individual LED 18 corresponding to the analog signal level is activated, so that only a single LED 18 is activated for a given level of the analog signal.

Referring to FIG. 5, a first embodiment of a limit circuitry 40 is depicted in schematic form. This circuit includes a series of converters 112, 114, 116, and 118 V which combined with a series of AND gates 120, 122,

124, and 126 serve to decode the six-bit binary word h b read out of the A/D converter 36. The most significantbits b and b are read by the AND gates 120, 122 124, and 126, while th least significant bits b b b and 5 are read by the converters 112, 114, 116, and 118. Each of the converters-112, 114, 116, and 118 is of the type which function'to convert a four-bit, binary word to low outputs at one of 16 outputs, each corresponding to a binary numberin the series capable of being represented by a four-bit word. lnthe present embodiment, however, the lower seven outputs of converter 112 and the upper six outputs of converter 118 are not utilized since only 51 increments, are used in the column.

The output of the AND gates 120, 122, 124, and 126 serves to inhibit any-output from each of the converters 112-118 which associatedtherewith if the output is high and will enable converters 112-118 ifthe output is low. The b and b inputs are read in combinations inverted and not inverted such that if b, and b are zero, converter'112 is allowed to produce outputs 07-15, if b, is one and b is zero, converter 114 is allowed to produce outputs 16-31, if b, is one and b is one, converter 116 is allowed to produce outputs 32-47, and if both b and 12 are 'one" converter 118 is allowed to produce its outputs 48-57. This it can be seen that this arrangement in effect produces a six-bit conversion of the binary number into 51 respective low states at the outputs of the converters 112-118.-These outputs are used to set the upper and lower limits by means of a slide wire system 128 which functions to allow selective connection of the converter 112-118 outputs which are connected to series of slide wire contacts 130 via line 132 to ,a pair of flip-flops 134 and 136.

Flip-flop 134 functions to trigger the reject indicator 22 whenever the binary signal increases to the value corresponding to that of the high value of these two contacts 132 engaged by a slidable contact 138. The slidable contact 138 includes a pair of contact elements 140 and 142 structurally joined to move together but Similary, flip-flop 136 functions to trigger the reject indicator 22 whenever the binary signal declines to the value corresponding to that of the lower value of these two contacts 132 engaged by a slidable contact 152. Slidable contact 152 includes a pair of contact elements 154 and 156 structurally joined to move together but electrically insulated from each other and which serve to connect a respective contact 132 to conductive strips 160 and 158 respectively in turn respectively connected to the .l and K inputs of the flip-flop 136 via inverters 162 and 164. When the binary signal declines to the value corresponding to that connected by contact 154 flip-flop 136 is set to trigger the reject indicator 22. When the signal increases to the value corresponding to that connected by contact 156 the flip-flop 136 is reset to discontinue the reject indication.

In order to insure proper start-up operation with a zero signal level, a reset logic signal LR is applied upon turning on the power so that the upper limit flip-flop 134 is reset and the lower limit flip-flop 136 is set as indicated.

Referring to FIGS. 6 and 7, an alternate arrangement for providing the digital limit circuitry is shown, which involves simpler electronics than the version shown in FIG. 5.

This system depends on the operational restriction that the upper limits must always be set above scale (the binary signal corresponding to decimal number 32) and the lower limits below scale 0, the disadvantage of which limitation is offset to a great extent by the center adjust capability of the instrument. Since this restriction applies, five-bit binary code sources 166 and 168 (FIGS. 6 and 7) for the lower and upper limit respectively can be utilized for comparison purposes, since for all binary signals above decimal 32 (scale 0), the sixth bit b will be one, for all binary signals below decimal 32, this bit will be Zero. This one fewer bit allows for one fewer connecting conductor from the binary code sources 166 and 168 to the rest of the circuitry. Thus, for the lower limit, the binary code source 166 is set at a particular desired limit d d. and this value is compared in a comparator 170 with the six bits b b of the binary signal read from the A/D converter 36. The comparator 170 functions such that it will produce an output high state on line 172 whenever the binary signal is less than the value selectively set in the binary code source 166. This signal is used to set a flipflop 176 whenever the binary signal is less than that set in the binary code source 166 to trigger the reject indicator 22 under these conditions.

Similarly, as shown in FIG. 7, a five-bit selectively set binary code C C is compared with the six bits of the binary signal contained in the A/D converter 36 b h in comparator 178 which produces an output whenever the b b signal is greater than the C C value. This output is used to set a flip-flop 180 whenever an output is received from comparator 178 to thus trigger the reject indicator 22 whenever these conditions exist.

The binary code sources 166 and 168 could comprise a slidable bus bar grounding a binary pattern of conductive strips to form a binary code source, or any other such suitable arrangement, as is well-known in the art.

FIG. 8 shows a logic circuit for triggering the overrange LED 28. This includes a combination of the b b b and b bits in AND gate 184, and the inverted b and b bits in AND gate 186, the outputs of which are connected to the reset and set inputs of a flip-flop 188 as shown having its Q output inverted and connected to LED 28 so that whenever the flip-flop 188 is set the over-range LED 28 is caused to emit. The flip-flop 188 is set when the bits b,, 5 I2 and b go to one (indicating a binary signal 111010 corresponding to decimal 58) or greater and reset as soon as the bits b and b return to zero (indicating binary signal 1 l 1001, equivalent to decimal 57) or less.

From the above description, it can be appreciated that a column display of the level of variable electrical signals has been provided which does not involve complex moving parts, or unduly complex electronic circuitry, and which is of a nature lending itself to lowcost volume manufacturing techniques. Also, the appearance of the relative change in position of the single individual indicator element also resembles closely the appearance of a float in a column type air gage to minimize transitions of user reading facility.

Furthermore, the digital form of the limit comparison described herein eliminates the disadvantage of drifting digital reject triggering values described above.

It should also be appreciated that a great number of variations from these described embodiments are possible within the spirit of the invention, which is to be limited only by the scope of the following claims.

Therefore, what is claimed is:

l. A display arrangement for providing a visual display of the level of variable electrical analog signals comprising:

converter means generating corresponding digital signals from said analog signals;

display means responsive to said digital signals to provide a visual display corresponding to said generated digital signal values;

limit indicator means including an indicator and also including means responsive to the generation of a preset digital signal value to activate said indicator, including a digital signal source and comparator means comparing said digital signals to a preset value of said digital signal source whereby said indicator is activated in response to the generation of the same preset digital signal value notwithstanding drift in said converter means.

2. The display arrangement of claim 1 wherein said limit indicator means includes means for varying the preset digital signal value causing activation of said indicator.

3. The display arrangement of claim 1 wherein said display means includes:

a series of indicator elements;

means for consecutively changing states of individual indicator elements in said series in response to generation of each of said digital signals, whereby a visual display of the digital signal value is provided.

4. The system of claim 3 wherein said means consecutively changing states of individual indicator elements includes means activating individual indicator elements and means deactivating any preceding activated elements so that only a single indicator element in said series is activated for each digital signal whereby the relative position of the single activated individual indicator element in said series provides a visual display of the digital signal.

5. The system of claim 4 wherein said series of indicator elements is arranged vertically and wherein said means activating said indicator elements activates indicator elements consecutively upward in said vertical series in response to increasing digital signal levels and activates an indicator element consecutively downward in response to decreases in said digital signal levels, whereby the rise and fall of the relative position of said single activated indication element in said vertical series thereof provides a visual display of said digital sig nal levels.

6. The system of claim 3 wherein said indicator elements comprise light emitting diodes.

7. The system of claim 3 further including displacement transducer means generating said variable electrical analog signal as an indication of a displacement whereby said activated indicator element in said series of indicator elements provides a display of displacements indicated by said variable electrical analog signal.

8. The display arrangement of claim 1 wherein said limit indicator means responsive to the generation of preset digital values above or below preset digital values to define upper and lower limit indications.

9. The display arrangement of claim 3 further including at least one adjustable limit indicator providing an indication along the series of indicator elements of the preselected limit set by said limit indicator means. 

1. A display arrangement for providing a visual display of the level of variable electrical analog signals comprising: converter means generating corresponding digital signals froM said analog signals; display means responsive to said digital signals to provide a visual display corresponding to said generated digital signal values; limit indicator means including an indicator and also including means responsive to the generation of a preset digital signal value to activate said indicator, including a digital signal source and comparator means comparing said digital signals to a preset value of said digital signal source whereby said indicator is activated in response to the generation of the same preset digital signal value notwithstanding drift in said converter means.
 2. The display arrangement of claim 1 wherein said limit indicator means includes means for varying the preset digital signal value causing activation of said indicator.
 3. The display arrangement of claim 1 wherein said display means includes: a series of indicator elements; means for consecutively changing states of individual indicator elements in said series in response to generation of each of said digital signals, whereby a visual display of the digital signal value is provided.
 4. The system of claim 3 wherein said means consecutively changing states of individual indicator elements includes means activating individual indicator elements and means deactivating any preceding activated elements so that only a single indicator element in said series is activated for each digital signal whereby the relative position of the single activated individual indicator element in said series provides a visual display of the digital signal.
 5. The system of claim 4 wherein said series of indicator elements is arranged vertically and wherein said means activating said indicator elements activates indicator elements consecutively upward in said vertical series in response to increasing digital signal levels and activates an indicator element consecutively downward in response to decreases in said digital signal levels, whereby the rise and fall of the relative position of said single activated indication element in said vertical series thereof provides a visual display of said digital signal levels.
 6. The system of claim 3 wherein said indicator elements comprise light emitting diodes.
 7. The system of claim 3 further including displacement transducer means generating said variable electrical analog signal as an indication of a displacement whereby said activated indicator element in said series of indicator elements provides a display of displacements indicated by said variable electrical analog signal.
 8. The display arrangement of claim 1 wherein said limit indicator means responsive to the generation of preset digital values above or below preset digital values to define upper and lower limit indications.
 9. The display arrangement of claim 3 further including at least one adjustable limit indicator providing an indication along the series of indicator elements of the preselected limit set by said limit indicator means. 